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;------------------------------------------------------------------------------
;
; Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
; SPDX-License-Identifier: BSD-2-Clause-Patent
;
; Module Name:
;
; LongJump.Asm
;
; Abstract:
;
; Implementation of _LongJump() on IA-32.
;
;------------------------------------------------------------------------------
%include "Nasm.inc"
SECTION .text
extern ASM_PFX(PcdGet32 (PcdControlFlowEnforcementPropertyMask))
;------------------------------------------------------------------------------
; VOID
; EFIAPI
; InternalLongJump (
; IN BASE_LIBRARY_JUMP_BUFFER *JumpBuffer,
; IN UINTN Value
; );
;------------------------------------------------------------------------------
global ASM_PFX(InternalLongJump)
ASM_PFX(InternalLongJump):
mov eax, [ASM_PFX(PcdGet32 (PcdControlFlowEnforcementPropertyMask))]
test eax, eax
jz CetDone
mov eax, cr4
bt eax, 23 ; check if CET is enabled
jnc CetDone
mov edx, [esp + 4] ; edx = JumpBuffer
mov edx, [edx + 24] ; edx = target SSP
READSSP_EAX
sub edx, eax ; edx = delta
mov eax, edx ; eax = delta
shr eax, 2 ; eax = delta/sizeof(UINT32)
INCSSP_EAX
CetDone:
pop eax ; skip return address
pop edx ; edx <- JumpBuffer
pop eax ; eax <- Value
mov ebx, [edx]
mov esi, [edx + 4]
mov edi, [edx + 8]
mov ebp, [edx + 12]
mov esp, [edx + 16]
jmp dword [edx + 20] ; restore "eip"
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